(a). Field of the Invention
The present invention relates to image processing, and more particularly, to an apparatus and method for adjusting image frames.
(b). Description of the Related Arts
When a video image (e.g. film) varies frequently or drastically, it is easy to result in undesirable visual effects, such as harsh screen flash, or insufficient contrast among a series of image frames, both of which causes obstruction to audience enjoyment. Thus, it is necessary to perform an image adjustment (contrast enhancement or reduction) before displaying this type of image with significant variation.
FIG. 1A and 1B are diagrams illustrating examples for adjusting the varying image. In FIG. 1A and 1B, the horizontal axis represents the order of image frames to be sequentially displayed, while the vertical axis represents the pixel value at a specific location (denoted by two dimensional coordinates (a, b)) of the various frames. The solid and dotted lines represent the pixel values before and after image adjustment respectively. In FIG. 1A, the pixel value remains less varied before frame 2, and increases drastically from frame 2 to frame 3. Thus, the adjusted pixel value is higher than the original one, thereby enhancing the contrast of the pixel. In FIG. 1B, the pixel value varies up and down violently. If the pixel is displayed directly, harsh flash effect occurs at this location of the image frame. Thus, the pixel value is adjusted to smoothen its variation, thereby reducing the contrast of the pixel and accordingly the undesirable visual effect.